Fuel injector



A ril 2, 1963 Filed D60. 1, 1960 R. L. SHALLENBERG FUEL INJECTOR 4 Sheets-Sheet 1 Faber! Z. SfiallehZe r y April 271963 R. L. SHALLEN BERG FUEL INJECTOR 4 Sheets-She et 2 Filed Dec. 1, 1960 R. L. SHALLENBERG 3,083,912

FUEL INJECTOR 4 Sheets-Sheet 3 QMV INVENTOR. fgzllenfiezfg c/Qfiy v9 mmmw m mm mm mm 5 mm mm mm kw mu AprH 2, 1963 Filed Dec. 1, 1960 mm vw m MWN R. 1.. SHALLENBERG 3,083,912

FUEL INJECTOR 4 Sheets-Sheet 4 8 w v 7 2 w l 6 INVENTOR.

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Patented Apr. 2, l fiizl 3,933,912 FUEL INFEETUR Robert L. Shallenherg, Wheaten, ilL, assignor to international Harvester Company, Chicago, TEL, a corporation of New Jersey Filed Dec. 1, race, Ser. No. 72352 (Ilaims. (\Cl. 239-433) This invention relates to fuel injector means for internal combustion engines and in particular relates to a hydraulically operated fuel injector for use in a diesel engme.

Presently designed fuel injectors are not capable of roviding higher atomiz-ing pressures through the injection nozzles into the combustion chamber Where and when required and the rate of fuel injection is a function of engine speed and cannot be controlled independently. This is equally true for a conventional cam operated pump and for rocker actuated injectors which provide a stereotyped mechanical injection employing mechanical linkage including a cam, tappet, push rod and rocker arm. The novel hydraulically actuated fuel servo-injector disclosed herein abrogates the aforementioned disadvantages of other types of injectors providing a widely variable range of injection pressures and rates.

it is therefore an object of this invention to provide a fuel injector that controls the pressure of the fuel injection and thus the rate of injection into an internal combustion engine at all speeds.

It is another object of this invention to provide a fuel servo-injector capable of developing extremely high injection pressures.

It is another object of this invention to provide an engine fuel injector supplied with low pressure operation to effect high pressure injection of the fuel from the injection nozzle.

Still another object of this invention is to provide a fuel injector including a servo-valve mechanism responding to fluid pressure from a fuel metering source with subsequent high hydraulic fluid pressure injection.

A further object of this invention is to provide a fuel injector comprising a servo-injection mechanism subjected to fluid pressure from a metered quantity of fuel for operation of said mechanism pursuant to the introduction of fluid under high pressure to perform a fuel injection stroke.

Another object is to provide a source of metered fluid pressure, a source of low pressure fluid for injection, and a source of high fluid pressure for operation of the metering and injection stroke of the servo-mechanism of the fuel injector.

Another object of this invention is to provide a fuel injector having a servo-injector mechanism subjected to a first metering fluid pressure source for initiating movement of the mechanism and a second low pressure fluid source for insuring a complete change of fuel for injec tion into the engine and a third high pressure fluid source for moving the servo-mechanism to inject the fluid into the engine.

These and other objects of this invention will become apparent from a reference to the following disclosed drawings and description which illustrate an embodiment that the invention may take, such embodiment however is not to be construed as a limitation upon the breadth or scope of the appended claims.

FIGURE 1 is a schematic view illustrating an internal combustion engine having a servo-injection system employing the fuel injector;

FIGURE 2 is a diagrammatic view of the fuel injection system illustrating the various sources of pressure for operation of the fuel injector;

FIGURE 3 is a view partly in cross section of the fuel injector shown in FIGURE 1;

FIGURE 4 is a View of a diagram illustrating the relation between hydraulic fluid pressure and time of injection employed in the novel fuel injector;

FIGURE 5 is a sectional view taken along line 5-5 of FIGURE 3, and

FIGURES 6 through 9 are views partly in cross section of the fuel injector as similarly shown by FIGURE 3 and illustrate various positions of the parts of the fuel injector during various operational stages.

With reference now to the drawings there is shown an internal combustion engine 1 of the diesel type carrying a fuel injection system 2 including a fuel tank 3 with fuel tank outlet line 4 having divided flow [through branch 5 to housing 6 carrying primary pump 7 and metering pump 8 and branch 9 carrying the fiuid or fuel it) to the high pressure supply pump ll. Inlet line 12 leading from the primary pump supplies the fluid It under pressure to the metering pump 8 and has communicating with it bypass line 13 having a check valve M therein set for psi. for returning fuel back to the inlet side 15 of the primary pump '7 when the pressure exceeds 90 psi The metering pump 8 may be of a rotary type fuel injection pump for supplying a metered quantity of fuel to the fuel injector 16 under pressure in a conventional manner having alternating periods of delivery and non-delivery of fluid under pressure thereto as shown in US. Patent No. 2,947,299. Fuel 17 thus may pass through conduit 1% into the injector 16 or through line 18a to tank 3. A fuel return line 19 communicates with the inlet line 12 of the metering pump 8 and bypass line 14 and with each of the six fuel injectors 16 through each of their respective conduits 2i). Similarly fuel line 21 communicates fluid under high pressure from the supply pump 11 to each of the injectors 16 through each of the high pressure inlet lines 22 of each of the injectors 16.

Reference now is directed in particular to FIGURE 3 and FIGURE 5 wherein there is shown a fuel injector 16 comprising a body or housing 23 having a servo-injector mechanism 24 at its right end and a nozzle assembly 25 at its left end and a metering passage 26 within the hollow member 24a of the servo-injector mechanism 24. The passage 26 communicates between the left end 27 of the pilot valve 28 and the metering line 18, and low pressure passages 29, 3t and 31 in the member 24 communicate with the fuel return lines 20 and 19', and a high pressure passage 32 in the member 24 communicates with lines 22 and 21, passage 32 being an extension of line 22 within the injector 16. The member 24a of the housing 23 of the injector 16 also has a central bore 34 having an annulus 35 adjacent a reduced bore portion 36 and an enlarged bore portion 37, the pilot valve 28 having first, second and third lands 38, 3% and 4b with reduced shank portions 41 and 42 between the lands 38, 39 and 4d, and said valve 23 being reciprocal .within a sleeve or power piston 43 housed and reciprocal within the bore 34 and carrying a tension spring 44 about its outer right end peripheral end portion 4-5, the other end 46 of the tension spring 44* being fastened to the extension 47 integral with the member 24:; of the injector 16. Ports 43a and 43b in right end of piston 43 and space 430 between piston 43 and extension 4-7 allow fluid communication between areas 37a and 37b of bore portion 37 of bore 34. The extension 47 has a hollow cup portion 43 at its left end 48a through which extends projection 49 integral with the extension 4-7 and carrying a compression spring 53 about its outer periphery engaging with the right end 52 of the pilot valve 28 for urging it to the left as viewed in FIGURE 3. Ports A, B and C Within the power piston '43 have selective communication with passages 29, 32 and 3t respectively, and the right end 52 of the pilot valve 28 has a central passage 54 having an outlet or port 54a in a groove formed by valve shank portion 42 allowing communication between the portion 37a of the bore 34 of the injector mechanism 24 and the passages B and C in certain positions of the pilot valve 28 and power piston 43. The annulus or recess portion 35 of the servo mechanism bore 34 has passages 57 and 58 communicating the annulus 35 with the nozzle channels 59 and 60 in the spring retainer member '61 housed within hollow member 62 of the nozzle assembly 25. The spring retainer member 61 houses spring 63 which urges collar 64 against the stem 65 of the nozzle plunger 66 having a head 67, nozzle valve 68, engageable with valve seat 69. The nozzle valve 68 is reciprocal Within the bore 70 of the nozzle end stfuctu're 71 housed within the hollow nozzle member 72 of housing 23. The nozzle end structure 7l has injectioh orifices 73 at its left end 74 communicating fluid from the annular bore 75, passage 76, annular port 77 of the nozzle structure 71 and passages 59, 60 into the cylinde'r 78 of the engine 1 carrying engine piston 79.

Operation of the fuel injector in FIGURE 3 shows the valve 28 at a point between its spill position and the charge position. At the spill position when the metering pump 8 is spilling the fuel from line 17 by way of line 18a to the fuel tank 3, the pilot valve 28 will be urged against the left end side or stop 80 of the servo-injector bore 34 because of the'compression spring 50 at the right end portion of the servo-injector bore 34 and residual fluid pressure on the right side of the valve 28- from a preceding injection stroke. The power piston 43 will follow with the pilot valve 28 and assume the same location relative to the pilot valve 28 as that shown in FIGURE 3 and FIG- URE 8 because the port B has also on the previous injection stroke admitted fluid under pressure to the right side of the power piston 43. When the pump 8 begins its metering stroke (see FIGURE 6), fuel is delivered under 2000 p.s.-i. to the left end 27 of the pilot valve 28 by way of line 18 and passage 26 displacing the valve 28 to the right (see FIGURE 7) in a charge position uncovering ports A and C simultaneously and exposing low pressure fuel from the return line 19 to the annulus 35 and bore portion 37a at the ends of the power piston 43. The fuel pressure in' cavity 37a at the right end of the bore 34 of the servo-injector mechanism '24 being under residual high pressure from the previous injection stroke plus any increase in pressure by movement of valve 28 to the right tends to shift the piston 43 to the left to expedite the uncovering of the ports A and C. The high pressure in the right cavity 37a now drops to the low pressure in the return line 19 and actually transfers fuel out through port C and into port A in equal amounts and the additional fuel displaced by valve 28 from cavity 370 goes back into the fuel return line and back to line 19 to the metering pump 8 or to the inlet side of the primary pump 7 if the pressure should exceed psi. port A passes into annulus 35 for subsequent injection into the engine chamber 79. Since cavity 37ahas established the low pressure in line 19, the tension spring moves to the power piston to right closing off ports A and C for termination of fuel transference which is of extremely short duration (see FIGURE 3 or FIGURE 8). The advantage of connecting the fuel return line 19" directly to the metering inlet line 12 rather than back to the reservoir 3 is to maintain a positive pressure head for sending fuel through port A into the cavity 35. As the metering pump 8 ends its metering stroke, the pump 8 hits spill and causes a quick drop in pressure on the left side of the pilot valve 28 causing sudden movement of the valve 28 to the left closing ports A and C and opening port B as-a result of fluid pressure in the cavity 37a plus the action of the'compression spring 50 and fluid under high pressure is admitted through passageway 54' into cavity 37d by way of line 22, passage 32, port B, groove 55, and port 54a and is applied to the right end of both of the pilot valve28 and th'e'poweipiston" 43, the pilot valve being moved all The fuel transferred into the way to its stop 80 very rapidly while the power piston fluid displacement on the left is delivered by way of the nozzle valve 68 and into the engine because the fluid in annulus 35 and under high pressure by the movement of the power piston 43 is transferred along annulus 35 and passages 57, 59 and 76 into the nozzle chamber 70 urging the nozzle plunger 66 against nozzle spring 63' and unseating nozzle valve 68 (see FIGURE 9). Upon termination of the injection stroke the power piston 43 being forced further to the left blocks communication of the port B with annulus 55 in the pilot valve 28 so the ports A, B and C and the power piston assumes a position relative to the pilot valve 28 as shown in FIGURE 3 but with the piston valve against the stop 80 in a rest position awaiting the next successive metering stroke of the pump.

The amount of fuel displaced by the power piston and therefore the amount of fuel injected into the combustion chamber 78 is related to the amount of fuel metered by the pump 8 in proportion to the area of the right end surface 27 of the pilot valve to the annular area of the left end surface 81 of the power piston 43. In the embodimentshown in FIGUREB the area of the left end surface 81 of the power piston 4 is greater than the area of the left end surface 27 of the valve 28 so that more fuel is injected than is metered. Consequently a small metering pump can inject a greater quantity of fuel, that is, a small metering pump may be used to operate a large engine. By varying the areas of surfaces 81 and 27 of the power piston 43 and the pilot valve 28 respectively, the relation between the amount of fuel metered and the amount of fuel injected can also be varied.

Referring now to FIGURE 4 the graph shown plots the high pressure of fuel injection in 'p.s'.i. for the injection stroke of the power piston 43 versus the time of fuel injection in milliseconds as controlled. The quantity of fuel required is always the same for a given engine load, and since delivery is a function of the pressure and time of injection, the fuel delivery represented by curves I, II or III is always the same. Consequently by varying the pressure, and 'thus the time of injection; it can be ascertained which curve or pattern will give the best results for power and speed demand. In this way high engine efliciency may be obtained for variou'sengine loads by sensitive control of the hydraulic injection pressure and thusthe time of the injection which control is possible by the hydraulically actuated fuel injector disclosed herein and which is not possible with the mechanical rocker arm control injection heretofore discussed.

What is claimed is:

1, A fuel injector comprising a servo-injector and nozzle assemblies, the servo-injector assembly including a hollow body and a hollow power piston reciprocal therein, a pilot valve reciprocal within the power piston, a first c h amber at one end of the power piston and a' second chamber at the other end of the piston and at one end of the valve, a metered source of fluid under pressure having selective cornunication with the other end of the valve, a low pressure fluid source within the body, first port means in the piston communicating with the low pressure source within the body, first passage means in the valve selectively communicable with the first port means and the first chamber and second passage means in the valve selectively communicating with the first port means and the second chamber consequent upon movement of the valve by the metered fluid, a source of fluid under high pressure communicating with the body, second port means in the piston communicating with the high pressure source and the second chamber consequent upon termination of flow of the metered source and moving the piston with attendant injection of the fluid in the first'chamber into the nozzle assembly.

2. A fuel injector having a nozzle portion and a pump portion, the pump portion including a bore having a piston reciprocal therein and having a pair of opposed pumping chambers on opposite ends respectively of the bore, a free floating valve within the piston resiliently urged toward one of the chambers and communicating with said one of the chambers and forming an injection chamber with the piston, said piston comprising first port means having selective passage with the injection chamber and the other of said chambers and comprising second port means having selective passage with the valve and the other of the chambers, fluid metering means in communication with said one chamber and selectively supplying fluid under pressure for urging the valve toward the i other of said chambers, a low pressure fluid in the pump portion selectively communicable with the injection chamber and the other of said chambers by way of the first port means as the valve is urged toward said other of the chambers, and a source of high pressure fluid within the pump portion in communication with the other of said chambers by way of the second port means and valve upon termination of supplying fluid to the one chamber by the metering means moving the piston and valve toward the one of the chambers with attendant transfer of fluid from the injection chamber to the nozzle portion.

3. A fuel injector having a nozzle portion and a pump portion, the pump portion including a bore providing a pair of spaced apart pump chambers, a valve mechanism between the chambers including a piston reciprocal within the bore, a shuttle valve reciprocal within the piston and being between the chambers, an injection chamber receiving the piston and being in communication with the nozzle portion, first, second, and third fluid pressure sources having passage in the body, said piston having first port means in communication with the first source of fluid pressure and having second port means in communication With the second source of fluid, said valve having first passage means in communication with the second pump chamber and in communication with the first and second port means and having second passage means in communication with the injection chamber and selective communication with the first port means, said third pressure source provided with means communicating the third pressure source with the first chamber moving the valve in one direction relative to the piston for fluid transfer out of the second chamber and into the injection chamber and interrupting communication of the third pressure source with the firstchamber moving the valve in the other direction relative to the piston with transfer of fluid from the second pressure source to second chamber for movement of the piston concurrent with further movement of the valve in the other direction and consequential transfer of fluid from the injection chamber into the nozzle portion.

4. In a fuel injection assembly having fuel injection means, a combination metering and pressurizing means operatively associated with the injection means and including structure comprising :a chamber communicating with the injection means, plunger means operating within the chamber and operative to pump measured quantities of fuel from the chamber into the injection means, and means operative on the plunger having an initial stroke moving the plunger at a relatively slow rate and having a following stroke moving said plunger at an accelerated rate developing high pressure within said chamber to discharge fluid in said chamber into said injection means.

5. In a fuel injection system having fuel injection mean-s therefor and control means therefor for delivering metered quantities of fuel to the injection means and said control means including valve means having an initiating chamber and a reaction chamber and an ejection chamber and having valving controlled by admitting fluid to the chambers, means providing initiating fluid pressure and connectible with the initiating chamber and providing low fluid pressure and connectable with the reaction chamber and the ejection chamber for transference of fluid to the latter and-providing high fluid pressure and connectible with the reaction chamber for discharge of fluid from said ejection chamber.

6. The invention according to claim 5 and said means providing initiating, low, and high pressures including a 6 primary pump and a metering pump and fluid conducting means between the primary pump and the metering pump and having one way check valve means to the pump for maintaining the low pressure at a predetermined value.

7. In a fuel injection system having fuel injection means therefor and control means therefor for delivering metered quantities of fuel to the injection means and said control means including valve means having an initiating chamber and a reaction chamber and an ejection chamber and having valving controlled by admitting fluid to the chambers, means providing initiating fluid pressure and connecti-ble with the initiating chamber and providing a source of fluid connectible with the reaction chamber and the ejection chamber for transference of fluid to the latter and providing high fluid pressure and connectible with the reaction chamber for discharge of the fluid from said ejection chamber.

8. In a fuel injection system having fuel injection means therefor and control means therefor for delivering metered quantities of fuel to the injection means, the control means including valve means having a pair of pump chambers and a metering chamber and having valving disposed between the pump chambers and controlled by admitting fluid to the chambers, means providing initiating fluid pressure and connectible with one of the pump chambers and providing a source of fluid and connectible with the other pump chamber and the metering chamber for transference of fluid out of the other pump chamber and into the metering chamber and providing high fluid pressure and connectible with the other pump chamber for discharge of fluid from said ejection chamber to the injection means.

9. In a fuel injection system having fuel injection means therefor and control means therefor for delivering metered quantities of fuel to the injection means, the control means including valve means having a pair of pump chambers piston means to pressurize the other pump chamber, second means providing fluid to other pump chamber and the metering chamber for transference of fluid to the latter, and third means providing secondary fluid pressure to the other pump chamber moving the piston means toward the metering chamber to discharge fluid from the latter to the injection means.

10. In a fuel injection system having fuel injection means therefor and control means therefor for delivering metered quantity of fuel to the injection means, the control means including valve means having a pair of pump chambers and a metering chamber and piston means and valving in fluid obstructing position between the one pump chamber and the metering chamber, means providing fluid pressure to the other pump chamber a predetermined time moving the piston means pressurizing the one pump chamber and unseating said valving, a second means providing fuel communicable with the one pump chamber and the metering chamber transferring fluid out of one pump chamber and into the metering chamber in the predetermined time, a third means providing a second fluid pressure to the one pump chamber after the predetermined time urging the piston means toward the metering chamber ejecting fluid therefrom to the injection means.

11. In a fuel system having fuel injection means therefor and control means therefor for delivering of metered quantity of fuel to the injection means, the control means including valve means and a pair of pump chambers and an ejection chamber, and piston means movably disposed between the pump chambers into first and second positions and having connection with the ejection chamber, said piston means and valve means forming first valving with the one pump chamber and the ejection chamber and forming second valving'with the piston means and the one pump chamber, means providing initnating pressure andconnectable with the other pump chamber for predetermined period moving the piston means from the first position to the second position pressurizing the one pump chamber was subsequent unseating of said first valving, means providinga fuel source and connectable with the first valving transferring fuel out of said one chamber and into said ejection chamber pursuant to the unseating of said first valving, and means providing a secondary pressure and connectable with said second valving, the piston means moving from said second position toward the first positionupon terminatidn of the predetermined period seating of the first valving and uns'eatiug the second valving with consequential pressur'izing of the one pump chamber by the secondary pressure accelerating the piston means to the first position and transferring fuel from the ejection chamber to the inection means. I

12 For operating fuel injection structure such as described, the combination of a fuel injector and a reservo ir and first and second and metering pumps and fluid conducting means therebet'ween, said fluid conducting means having a first conduit from the reservoir to the inector supplying fluid for injection, the first conduit including a first pumpinlet line to the first pump and a second inlet line to the second pump, said fluid conducting means having a second conduit between the first pump and the metering pump and a third conduit from the second pump to the injector and a fourth conduit from the metering pump to the injector and a return line from the metering pump to the reservoir, said first pump developing an initiating pressure for transferring a metered quantity of fuel within the injector in a predetermined period and said second pump developing a high pressure for rapid ejection of the metered fuel from the injector. v p

'13. For operating fuel injection structure as described including a fuel injector having a fluid-rleceiving means and a fluid ejection chamber, the combination of a fluid reservoir, a primary pump having fluid communication with the reservoir and delivering fluid under low pressure to the receiving means, a metering pump having communication with the primary pump receiving fluid from the latter and having communication with the injector transferring a given quantity of fluid from the fluid-receiving means to the ejectionpchamber in a predetermined time, and a secondary high pressure pump receiving fluid from the reservoir and having pressure communication with the ejection chamber and providing rapid ejection 'of the metered fluid therefrom.

14. For operating fuel injection structure such as described including a fuel injector having a' fluid-receiving means and a fluid ejection chamber, the combination of a fluid reservoir, a primary pump having fluid communication with the reservoir and delivering fluid under low pressure to' the receiving means, a metering pump having communication with the primary pump receiving fluid from the latter and having communication with. the injector transferring a given quantity of fluid from the fluid receiving means to the ejection chamber in a predeter- 'mined time, and a secondary high pressure pump receiving fluid from the reservoir and having pressure communication with the ejection chamber andprovidingrapid ejection of the metered fluid therefrom and said primary pump having an inlet and outlet and fluid conducting means connected between inlet and outlet and provided with pressure limiting means having fluid communication with the receiving means for establishing a predeterminedpositive pressure in the latter means. I

15. For operating fuel injection structure such as described including' a fuelinjector having primary and secondary chambers; the combination of afluid source, a

, primary pump having communication 'with the source and delivering fluid at one pressure to the primary chemher, a metering pump receiving fluid from thei'primary pump and having fluid pressure communication with the injector and providing means transferring fluid in predetermined .am'o'unts' out of the primary chamber and into the secondary chamber, and a secondary pump having communication with the source and delivering fluid at another pressure to the primary chamber for ejection of the fluid from the secondary chamben v A tFor operating fuel injection structure such as-described including a fuel injector having primary and secondary chambers, the combination of a fluid source, a. primary pump havingcotnmunication with the source and delivering fluid at one pressure to the primary chamber, a metering pump receiving fluid from the primary pump and having fluid pressure communication with the injeotor and providing means transferring fluid in predetermined amounts out of the primary chamber and into the secondary chamber, and a secondary pump having communication with" the source and delivering fluid at another pressure to the primary chamber for ejection of the fluid from the secondary chamber, and said primary pump having an-inlet and outlet, and fluid conducting means therebet'ween having fluid communication with the primary chamber and having means maintaining the pressure therein at a positive predetermined value providing a pressure head for the primary chamber.

17. A control assembly for a fuel injection means comprising a housing having an elongated bore and provided with an ejection chamber, piston means reciprocal within the bore and forming first and second chambers one at each end thereof with the bore, said bore and piston r'nejans providing valve means cornmunicatingbetween the first chamber and the ejection chamber, and intermittently acting means having first and second posit-ions and providing initial pressurizing and connectible with the second chamberand operative of the piston means to unseat the valve means andtransfer fluid out of the first chamber and into the ejection chamber in the first position and close the valve in the second position, and other means providing secondary pressurizing and connectible with the first chamber and operative of the piston means to expel fluid out of the ejection chamber in the second posit'ion of the intermittently acting means. 7

18. A fuel injector mechanism having an injection unit and a servo-injection mechanism for transferring fuel to the former, the mechanism comprising a housing having a bore with a reduced endportion, a member reciprocal within the bore and extendable into the end portion formirig a first chamber therewith and forminga second chamber at the opposite end of the member with the 'bore, ram means forming with the bore and the member a third chamber communicable with the injector unit and first valve means having connection with the second and third chambers and second valve means having connection with the second chamber, means providing initiating pressure at timed intervals and connectable with the first chamber for expanding s'ame'and compressing and pressurizing the second chamber and unseating the first valve means, and a source of fuel havingcommunication with the first valve means and regulative for transferring fuel out ofthe second chamber and" into the third chamber in substantially equal amounts as the second chamber is compressed, and means providing secondary accelerating pressure to the second valve means andoperative to expand the second chamber upon termination of the initiating pressure, with consequential seating of the'first valve'means and unseatingof the second valve means with attendant expansion of the second chamber and compression of the. third chamber by the ram means for rapid transfer of fuel from the third chamber to the injectorunit.

19'. A fuel injector mechanism having an injection unit and a servo injection mechanism for transferring fuel to the for-mer, -the mechanism comprising a housing having a bore with a reduced end portion, a member reciprocal within the bore and extendable into the end portion forming a first chamber therewith and forming a second chamber at the opposite end of the member with the bore, and biasing means within the bore urging the member toward the first chamber, ram means forming with the bore and the member a third chamber communicable With the injector unit and first valve means having connection with the second and third chambers and second valve means having connection With the second chamber, means providing initiating pressure at timed intervals and connectible with the first chamber 'for expanding same against the biasing means and compressing and pressurizing the second chamber and unseating the first valve means, and a source of fuel having communication With the first valve means and regulative for transferring fuel out of the second chamber and into the third chamber in substantially equal amounts as the second chamber is compressed, and means providing secondary accelerating pressure to the second valve means and operative to expand the second chamber upon termination of the initiating pressure with consequential seating of the first valve means and unseating of the second valve means with attendant expansion of the second chamber and compression of the third chamber by the ram means for rapid transfer of fuel from the third chamber to the injector unit.

20. A fuel injector mechanism having an injection unit and a servo-injection mechanism for transferring fuel to the former, the mechanism comprising a housing having a bore with a reduced end portion, a member reciprocal within the bore and extendable into the end portion forming a first chamber therewith and forming a second chamber at the opposite end of the member with the bore, ram means forming with the bore and the member a third chamber communicable with the injector unit and first valve means having connection with the second and third chambers and second valve means having connection with the second chamber, and a connection between the second chamber and the ram means allowing the ram means to follow movement of the member, and a connection between the member and the ram means allowing the ram means to follow movement of the member, means providing initiating pressure at timed intervals and connectible with the first chamber for expanding same and compressing and pressurizing the second chamber and unseating the first valve means, and a source of fuel having communication with the first valve means and regulative for transferring fuel out of the second chamber and into the third chamber in substantially equal amounts as the second chamber is compressed, and means providing secondary accelerating pressure to the second valve means and operative to expand the second chamber upon termination of the initiating pressure with consequential seating of the first valve means and unseating of the second valve means with attendant expansion of the second chamber and compression of the third chamber by the ram means for rapid transfer of fuel from the third chamber to the injector unit.

References Cited in the file of this patent UNITED STATES PATENTS 1,934,296 Dorner Nov. 7, 1933 2,656,854 Douglas et al. Oct. 27, 1953 2,690,356 Berlyn Sept. 28, 1954 2,793,077 Bovard May 21, 1957 2,856,023 Graves Oct. 14, 1958 

4. IN A FUEL INJECTION ASSEMBLY HAVING FUEL INJECTION MEANS, A COMBINATION METERING AND PRESSURIZING MEANS OPERATIVELY ASSOCIATED WITH THE INJECTION MEANS AND INCLUDING STRUCTURE COMPRISING A CHAMBER COMMUNICATING WITH THE INJECTION MEANS, PLUNGER MEANS OPERATING WITHIN THE CHAMBER AND OPERATIVE TO PUMP MEASURED QUANTITIES OF FUEL FROM THE CHAMBER INTO THE INJECTION MEANS, AND MEANS OPERATIVE ON THE PLUNGER HAVING AN INITIAL STROKE MOVING THE PLUNGER AT A RELATIVELY SLOW RATE AND HAVING A FOLLOWING STROKE MOVING SAID PLUNGER AT AN ACCELERATED RATE DEVELOPING HIGH PRESSURE WITHIN SAID CHAMBER TO DISCHARGE FLUID IN SAID CHAMBER INTO SAID INJECTION MEANS. 